SPHiEROPSIS. 



[ 589 J 



SPHiEROZYGA. 



of these spores, which is interesting in seve- 

 ral respects. Their ordinary size is from 

 l-1200to 1-1500", and they present, as above 

 mentioned, two coats, the outer elegantly 

 marked; most authors describe it as stel- 

 late j Kiitzing asserts that it is spirally folded. 

 The real fact is, that it is plaited in the di- 

 rection of * meridians' from pole to pole, and 

 thus appears stellate when seen at one pole, 

 marked with lines when seen sideways. The 

 spores do not appear to germinate until the 

 spring following their production. The red 

 contents begin to assume a green colour 

 from the surface inwards, divide into two, 

 then into four or eight portions, which break 

 out from the spore-cell, and swim about as 

 free biciliated zoospores, of globular or 

 shortly cylindrical form, from 1-2280 to 

 1-1680" long, either bright red or parti- 

 coloured red and green, the point bearing 

 the cilia, however, always colourless. After 

 a time they become coated with a cellulose 

 membrane, cease to move, and grow into a 

 spindle-shaped body, the ends prolonged 

 into hair-like points. The growth appears 

 to be always in the middle, the hair-like 

 points remaining ; thus the spindle-shape is 

 retained until the length reaches 1-24" or 

 more, and the first septum appears in the 

 middle of the filament. 



iS. annulina (PL 5. fig. 14) appears to be 

 the only well-known form. It is a rare Con- 

 ferva, growing on flooded fields; it does 

 not seem to have been recorded in Britain. 



For Sph. crispa and punctata, see Ulo- 



THRIX. 



BiBL. Kiitz. Sp. Alg. p. 362, Tah. Phyc, 

 iii. pi. 31 ; A. Braun, Verjungung, Sfc. {Ray 

 Soc. Vol. 1853, p. 165); Cohn, Bericht. Ber- 

 lin. Akad. May, 1855. 



SPH^ROPSIS, Lev.— A genus of Sphge- 

 ronfemei (Coniomycetous Fungi), growing 

 upon stems, &c., apparently only stylospo- 

 rous forms of Sphseriaceous genera. 



BiBL. Fries, Summa Veget. p. 419. 



SPH^ROSIRA, Ehr. See Volvox. 



SPH^ROZOSMA, Corda.— A genus of 

 Desmidiaceae. 



Char. Filamentous ; filaments flat, fra- 

 gile ; their component cells closely united 

 by means of minute (glandular) processes, 

 and deeply divided on each side into two 

 segments. 



(S. vertebratum (PI. 10. fig. 9, front view; 

 fig. 10, side view). Cells about as long as 

 broad; connecting processes oblique, one 

 on each side. Length of cell 1-1430". 



Not uncommon. 



/S. excavatum. Cells longer than broad ; 

 connecting processes sessile, two on each 

 side. Length of cell 1-25/0". 



After separation the cells conjugate ; spo- 

 rangia elliptical. 



BiBL. Ralfs, Brit. Desmid. 65. 



SPHiEROZYGA, Agardh {Anabaina, 

 Bory, Brebisson). — A genus of Nostochacese, 

 difi^ering from the allied genera only in the 

 microscopic characters of the filaments, the 

 spermatic cells being separated by vesicular 

 cells. As the spermatic cells are developed 

 from the ordinary cells, and this gradually, 

 the vesicular cell will appear at certain epochs 

 to have a spermatic cell on one side, and an 

 ordinary cell on the other ; but this arises 

 merely from the fact that the spermatic cells 

 are developed singly and successively, first 

 one on one side of the vesicular cell and then 

 one on the other, and so on to whatever 

 number of adjacent spermatic cells there 

 may be developed on either side of the vesi- 

 cular cell, and those nearest the latter will 

 therefore always be the largest, until the 

 whole have acquired the full size. Ralfs 

 describes seven British species. 



* Filaments moniliform, sporangia elongated, 

 not turgid. 



1. S. Carmichaelii, Harvey. — Filaments 

 with tapering extremities ; ordinary joints 

 distinct, subquadrate; spermatic cells ob- 

 long; vesicular cells spherical. — Ralfs, Anfi. 

 Nat. Hist. ser. 2. v. pi. 8. fig. 7 ; Harvey, 

 Phyc. Brit. pi. 113 A, Br. Mar. Alga, 

 2nd ed. pi. 27- fig. D. 



Belonia torulosa, Carmichael ; SphcBrozyga 

 compacta, Kiitzing, Phyc. generalis. Ana- 

 baina marina, Brebisson ; Cylindrospermum 

 Carmichaelii, Kiitzing, Sp. Alg. 2.94, Tab. 

 Phyc. i. pi. 99. 



Var. tenuissima,wiihyeYys\endev filaments. 

 Forming a tender, very thin stratum of a 

 dark or bluish -green colour on the damp 

 soil of salt-marshes flooded at spring-tides, 

 more rarely in brackish ditches or upon 

 decaying marine Algae. 



The best distinctive marks of this species 

 are the " subacute extremities combined with 

 the short filament and littoral habit." 



2. S. Jacobi, Agardh. — Filaments elon- 

 gated, their ends usually attenuated ; ordi- 

 nary cells subspherical; vesicular cells sphe- 

 rical; spermatic cells oblong or cylindrical. — 

 Ralfs, I.e. pi. 8. fig. 8; Eng. Bot. 2826. fig. 2. 

 Forming thick, bluish-green, gelatinous 

 masses, from which the filaments issue in 

 long rays. Fresh water. 



